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Heat

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  1. 2 Heat Calories Temperature Celsius Thermometer Specific Heat Fahrenheit Absolute Zero

  2. Temperature Temperature is a measure of how hot or cold an object is Ice Water 0o C 32o F 273o K 212o F 373o K Boiling Water 100o C 310o K 37o C 99o F Body Temp 68o F 293o K 20o C Room Temp -459o F 0o K Absolute Zero -273o C K = C + 273 F = 9/5 C + 32

  3. Pressure and Temperature 0o C 100o C Constant Air Volume Pressure Decreases Pressure Increases Pressure Gage Boiling Water Ice Water

  4. Absolute Zero Boiling Water 373o K 0o C 100o C Ice Water 273o K Temperature (o C) -273o C AbsoluteZero 0o K

  5. Quantity of Heat Quantity of Heat = Mass x Specific Heat x Temperature Change Q = m c ΔT 1 calorie is the amount of heat energy necessary to raise 1 gram of water 1 celsius degree. Specific Heat (Capacity) is the amount of heat energy necessary to raise 1 gram of a substance 1 celsius degree. 1 calorie = 4.18 joules 1 Calorie = 1,000 calories = 4,180 joules

  6. Hot Object Cold Object Heat Flow Calorimetry Heat Loss = Heat Gain mH cHΔTH = mC cCΔTC mH = mass of hot object cH = specific heat of hot object ΔTH = temperature change of hot object mC = mass of cold object cC = specific heat of cold object ΔTC = temperature change of cold object

  7. Hot Object Cold Object Heat Flow Sample Problem 1 500 g of metal at 90.0o C is placed in 200 g of water at 10.0o C. The specific heat capacity of the metal is .30 cal/goC. What is the final equilibrium temperature of the water and metal? Heat Loss = Heat Gain mH = 500 g TH = 90.0oC CH = .30 cal/goC mC = 200 g TC = 10.0oC CC = 1.0 cal/goC TE = ? mH cHΔTH = mC cCΔTC 500(.30)(90- TE) = 200(1.0)(TE - 10) 150 (90- TE) = 200 (TE - 10) 13500- 150TE = 200 TE - 2000 350TE = 15,500 TE = 44.3 oC

  8. Cold Water Hot Metal Sample Problem 2 800 g of metal at 100.0o C is placed in 200 g of water at 10.0o C. The final equilibrium temperature of the water plus metal is 40.0oC. What is the specific heat capacity of the metal ? Heat Loss = Heat Gain mH = 800 g TH = 100.0oC mC = 200 g TC = 10.0oC TE = 40.0oC CC = 1.00 cal/goC CH = __ cal/goC mH cHΔTH = mC cCΔTC 800 (CH)(100- 40) = 200(1.0)(40- 10) 48,000 (CH) = 6,000 CH = .125 cal/goC

  9. ThermalExpansion

  10. Lo ΔL Linear Expansion ΔL = is proportional to ΔT ΔL = is proportional to Lo ΔL = depends on the type of material

  11. Volume Expansion ΔV = is proportional to ΔT ΔV = is proportional to Vo ΔV = depends on the type of material

  12. Linear Expansion The following materials are listed in alphabetical order. Arrange them in order of their rate of linear expansion per oC from lowest to highest. • Aluminum 2.4 cm per km • Brass 2.0 cm per km • Copper 1.7 cm per km • Steel 1.2 cm per km • Glass 0.4-0.9 cm per km Aluminum Brass Copper Glass Steel

  13. Expansion of Water

  14. Heat Transfer Conduction - Molecule to Molecule Convection - Movment of Fluids Radiation - Electomagnetic Waves

  15. TH TC H L Conductivity H is the heat flow between hot (TH) and cold ( TC) objects H increases as (TH – TC) increases H decreases as L increases H = depends on the type of material

  16. Top 7 Conductors of Heat The following metals are listed in alphabetical order. Arrange them in order of conductivity from best to worst. • Silver 406 • Copper 385 • Aluminum 205 • Brass 109 • Steel 50 • Lead 35 • Mercury 8 Aluminum Brass Copper Lead Mercury Silver Steel

  17. Top 10 Heat Insulators The following insulators are listed in alphabetical order. Arrange them in order of insulation from best to worst. Air Brick Concrete Cork Felt Fiberglass Glass Rock Wool Styrofoam Wood • Styrofoam .01 • Air .024 • Cork .04 • Felt .04 • Fiberglass .04 • Rock Wool .04 • Wood .12 • Brick .6 • Concrete .8 • Glass .9

  18. Day Night Sea Breezes and Convection Currents During the night, the land cools faster and the air rises above the warmer water and is replaced by the cooler air from above the land. During the day, the land is hotter and the air rises above the land and is replaced by the cooler air from above the water.

  19. Convection Currents and the Earth

  20. Radiation • A good radiator of heat is a good absorber of heat. • Dark colored objects radiate and absorb heat better than light colored objects. • The rate of heat radiation increases with temperature. • The rate of heat radiation or absorption is proportional to the surface area of the object radiating or absorbing.

  21. A= 6 cm2 Scaling and Heat Radiation A/V = 6 S = 1 cm V= 1 cm3 A = 24 cm2 S = 2 cm A/V = 3 V= 8 cm3 S= 10 cm A/V = .6 A = 600 cm2 V= 1000 cm3

  22. 2 Change of State Steam Ice Water Heat Heat 80 calories added to 1 g of ice at 0oC will convert the ice to 1gram of water at 0oC. 540 calories added to 1 g of water at 100oC will convert the water to 1gram of steam at 100oC.

  23. 3 Water to Steam Steam Ice to Water Water Ice

  24. External Work Food Heat Out Heat In Internal Work The Human Body -Thermodynamic System Energy Change = (Food +Heat In) – (External Work + Heat Out + Internal Work)

  25. External Work Food Heat Out Heat In Internal Work Thermodynamics and Weight Loss Energy Change = Food + Heat In – External Work - Heat Out - Internal Work If Energy Change = 0, then you maintain your body weight. If Energy Change> 0, then you gain weight. If Energy Change< 0, then you lose weight. If 1 once fat is equivalent to approximately 300 Calories of energy, we can calculate weight loss on a daily or monthly basis based on ΔU value.